1. Field of the Invention
This invention relates to an integrated filter circuit, and more particularly to one which includes a charge transfer device transversal filter.
2. Description of the Prior Art
Charge transfer devices are now widely recognized and understood. See, for example, the book by Sequin and Tompsett, "Charge Transfer Devices", Academic Press, New York, 1975. The invention of charge transfer devices offered an attractive possibility for analog signal processing. The charge transfer device and particularly the charge coupled device is essentially a clock controlled shift register for the transfer and storage of charge packets representing samples of an analog signal. Such a delay line with several input and output stages can be used to realize a variety of filter principles, one of which is implemented in the transversal filter. This type of filter has no closed loop. Thus, it has a finite impulse response and no stability problems are encountered. An interesting discussion of sampled analog filtering using switched capacitors as resistor equivalents is found in an article by J. Terry Caves et al in the "IEEE Journal of Solid State Circuits", Vol. SC-12, No. 6, December, 1977, pp. 592-599. Another article providing background is found in the publication Siemens Forschungs-und Entwicklungs-Berichte, Vol. 7, 1978, No. 3, pp. 138-142. The present applicant is one of the authors of this article.